1. Field of the Invention
The present invention is directed to a gas-dispensing device for dispensing a gas into a breathing gas, of the type having a membrane through which the gas can diffuse into the breathing gas. The invention also is directed to a breathing apparatus having such a gas-dispensing device.
2. Description of the Prior Art
In conjunction with respiratory care (with a respirator, ventilator, anesthetic machine or other breathing machine), the physician may sometimes wish to supplement the breathing gas with a medical gas. NO is an example of a medical gas, but there are other gases with a therapeutic or other effect (e.g. anesthetic, analgesic).
One way to dispense a gas is to utilize a membrane permeable to the gas. The rate of diffusion then governs the amount dispensed. Connecting a gas source containing the gas to be dispensed into the flow of breathing gas in a breathing apparatus via a membrane is known.
One disadvantage of this system is that the gas source may be bulky. Patient transport then becomes more difficult, or dispensing may need to be interrupted during transport. The gas source can also require more rigorous safety precautions to ensure that the gas source does not leak. This is the case for e.g. NO and anesthetic gases. In addition, the gas-dispensing system must be equipped to prevent overdosing, even if the membrane or some other component (e.g. a pressure regulator) should fail.
Another disadvantage of known techniques is that special monitoring equipment, or special pressures combined with fixed valves etc., are required if a specific total amount (a given amount of gas) is to be dispensed.